Traditionally, grouping time is the peak of respiratory disease, says Tom Shelton, veterinarian and senior technical services specialist with Intervet/Schering-Plough Animal Health. But the hutches the calves are in prior to grouping are not immune to respiratory disease either.

A vaccination protocol needs to be in place so calves are not carrying something into the group pens. If they appear to have a respiratory disease, a treatment plan has to be in place as they enter.

Research shows when group sizes get higher than seven, the risk of respiratory disease increases, Shelton added.